The present invention relates to novel copper formate complexes and the deposition of metallic copper on substrates or in or on porous solids using such copper formate complexes.
The deposition of copper from supercritical fluids has been described. Watkins and McCarthy, U.S. Pat. No. 5,789,027, used an external reducing agent such as hydrogen added to the supercritical fluid to promote copper deposition on a substrate (e.g., silicon wafer). Also, copper disproportionation reactions have been used (Hsu et al., Chemical Vapor Deposition, 2001, 7, No. 1, pp. 28-31).
Bernard et al. (Thermochimica Acta, 98, 139-145 (1986)) describe the formation of dimeric copper (ll) complexes with 1-methylimidazole by addition of copper formate to an ethanol solution containing an excess of 1-methylimidazole. The product precipitates rapidly from solution. It contains Cu(II) ions coordinated to three or four imidazole groups and water molecules. The formate ion is present as counter ion and does not coordinate to the copper ion. This formulation is unsuitable for use in supercritical fluids such as supercritical carbon dioxide because the copper complex has little or no solubility in non-polar solvents.
Escrivxc3xa1 et al. (J. Chem. Soc. Dalton Trans., 2033-2038 (1997)) describe a formate complex with monoatomic bridging formates.
Borel et al. (Rev. Chim. Miner., 17, 202-208 (1980)) describe the preparation and structure of a mononuclear copper formate complex with 2,6-lutidine.
Smith (U.S. Pat. No. 4,582,731) describes solid films deposited by dissolving a solid material into a supercritical fluid solution at an elevated pressure and then rapidly expanding the solution through a short orifice into a region of relatively low pressure.
Darr and Poliakoff (Chemical Reviews, 99, 495-542 (1999)) have shown that compounds soluble in hexane exhibit solubility in supercritical carbon dioxide and have described metal ligands that have been used for metal solubilization and extraction in supercritical fluids.
Smart et al. (Talanta, 44, 137-150 (1997)) have described the preparation of Cu(II) complexes which are soluble in supercritical carbon dioxide.
Cross et al. (Ind. Eng. Chem. Res., 35, 1765-1770 (1996)) describe the use of co-solvents in supercritical carbon dioxide to dissolve metal complexes.
Trofimenko (xe2x80x9cScorpionatesxe2x80x9d, Imperial College Press, 1999) reviews substituted pyrazole derivatives.
This invention provides a composition comprising copper, two formate ions coordinated to the copper, and two aromatic nitrogen heterocyclic ligands coordinated to copper through nitrogen, wherein the aromatic nitrogen heterocyclic ligands are selected from the group consisting of C10-C20 alkyl-substituted pyridines, C9-C20 alkyl-substituted pyrazoles, C9-C20 alkyl-substituted imidazoles and C9-C20 alkyl-substituted triazoles, in which the N1 position of the pyrazole, imidazole and triazole ligands are alkyl-substituted.
A process for deposition of metallic copper on a substrate or in or on a porous solid is also provided, comprising
a. contacting the substrate or porous solid with a copper complex of this invention to form a copper complex-coated substrate; and
b. heating the copper complex-coated substrate or porous solid to about 70xc2x0 C. to about 200xc2x0 C. to form a deposit of metallic copper on the substrate.